Metallic filament for incandescent lamps.



UNITED STATES I PATENT OFFICE.

CARL FARKAS, OF NEW YORK, N. Y., ASSIGNOR OF ONE-HALF 'IO HERMAN J. JAEGER, OF NEW YORK, N. Y., AND ONE-HALF TO CHARLEST. JAEGER, F BROOKLYN, NEW

YORK.

I 945,504. Specification of Letters Patent. 110 Drawing.

METALLIC FILAMENT FOR INCANDESCENT LAMPS.

Patented Jan. 4, 1910.

Application filed August 18, 1908. Serial No. 449,031.

, To all whom it may concern:

- dent of New Be it known that I, CARL FARKAS, a citi-- zen-of the Kin dom of Hungary, and a resiork, in the county and State of New York, have invented certa in new and useful Improvements in Metallic Filaments for Incandescent Lamps, of which the following is a specification.

This invention has reference to improvements in process of producing metallic filaments for incandescent electric lamps. It pertains to the production of such filaments in which a refractory coating is produced in 'vacuo onan inner conducting core, said coating being formed by decomposing vapors of salts by means of the electric current. For the purpose of effecting a rather quick decomposition of the salts for instance chlorid of chromium, I introduce simultaneously with such vapors or imme-,

diately thereafter some vapors of pyrogallol.

In .carrying the invention intov effect I substantially proceed as follows: A fin'e conducting core is placed between the clamps of a support to which current may be supplied. The support and conducting core are placed into one of'the well known receivers of glass from which the air is then exhausted. Now the vapors of chlorid of chromium, for instance, are introduced and preferably simultaneously therewith some vapors of pyrogallol. 3 By heating electrically the conducting core the vapors within the receiver are decomposed and a refractory coating produced thereon in a quick manner by virtue of the presence of the vapors of pyrogallol which latter is an organic substance and when its vapors are decomposed atomistic carbon is formed. The

carbon, in statu nascendi, acts'as a cementing means for a refractory coating just forming and while in the incandescent state. Probably chromium carbid is formed. Pyrogallol further acts as a reducing agent as pointed out further below. When the coatmg has thus been produced the vapors within the receiver'are removed and hydrogen gas is introduced in the usual manner and the refractory filament electrically heated whereby the coating or the deposition is reduced to metal. If desired the conductive core, when consisting for instance ofsilver, may be volatilized.

or carrying the above described process into effect the mixture of the vapors of chlorid of chromium and pyrogallol may have various proportions. The large bulk is certainly vapor of chlorid of chromium mixed with some vapors of pyrogallol for instance'of the first 93% per volume may be allowed to enter the receiver mixed with 7% of the latter The vacuum in the receiver, which at the start is about or slightly above 29 inches, willbe reduced bythe introduction of the vapors to about 20 inches. As to the action of the pyrogallol vapors it need hardly be mentioned that same is a great reducing agent and absorbs oxygen in considerable quantities. Thisv substance takes up the oxygen of the metal oxids of which the refractory coating is primarily composed whereby a partial reduction to metal is effected. When the coating has been produced as described the ,ex- 1 pors of a salt of a highly refractory metal in the presence of vapors of pyrogallol reducing thus the vapors of the salt to oxid, and finally reducing theoxid to metal in an atmosphere of hydrogen.

2. In a process of producing metallic filaments for incandescent'electrm lamps produced by forming a highly. refractory coating on a conducting core, the cementing of said coating and artial reduction of same to metal by simu taneously decomposing by the action of the electric current vapors of pyrogallol and completing the reduction in an atmosphere of hydro en.

Signed at New York, N. Y., this -1 th day LUDWIG K. Bonn, j HENRY BRADY. 

